1. Field of the Invention
The present invention relates to a liquid material evaporation apparatus for use in semiconductor manufacturing.
2. Description of Related Art
FIG. 5 shows the structure of the main portion of a conventional liquid material evaporation apparatus including a gas-liquid mixing chamber, a flow control portion, and a nozzle portion formed into one block for improved evaporation of a liquid material when the block is heated. In this drawing, the main body block 51 is in the shape of a rectangular parallelepiped.
Three flow passages 52, 53, 54 are formed inside the main body block 51. A gas-liquid mixing chamber 55 is formed in the upper surface.
The flow passage 52 is for introducing a liquid material LM (not shown) into the gas-liquid mixing chamber 55, and this liquid material introduction passage 52 is provided in a direction vertical to the surface of the drawing in the shape of a reverse-L character so that one end of the flow passage is opened to the front surface side of the main body block 51 and the other end is opened to the upper surface of the main body block 51. The flow passage 53 is for introducing a carrier gas CG into the gas-liquid mixing chamber 55. The carrier gas introduction flow passage 53 is in the shape of an L character so that one end is opened to the left side surface of the main body block 51 and the other end thereof is opened to a recess portion 51a of the upper surface of the main body block 51. The flow passage 54 functions as a gas discharge passage, with one end opened to the right side surface of the main body block 51, the other end is connected vertically up to an appropriate position of the main body block 51, and the upper end side is coupled to the gas-liquid mixing chamber 55 via a nozzle portion 56.
The gas-liquid mixing chamber 55 is formed so that the recess portion 51a formed on the upper surface of the main body block 51 is covered by a diaphragm 57 as a valve member. The diaphragm 57 is accommodated in a valve block 58 arranged on the upper surface of the main body block 51 and is driven downward towards the mixing chamber by means of a piezo actuator 59 extending upward on the upper portion of the valve block 58. Spring 60 constantly biases the diaphragm 57 upwardly. Heater 61 is for heating the main body block 51.
The nozzle portion 56 is dimensioned so that the diameter and length are 1.0 mm or smaller. The nozzle is located in close proximity to the end of the gas discharge passage 54 closest to the gas-liquid mixing chamber 55. The mixture of the liquid material and carrier gas passes through the nozzle portion 56 into the discharge passage 54 thereby becoming depressurized and evaporating into a mixed gas. This mixed gas flows to the downstream end of the discharge passage 54.
In the liquid material evaporation apparatus of the above-described structure, the liquid material LM and the carrier gas CG are mixed in the gas-liquid mixing chamber 55 provided in the main body block 51 which is heated to an appropriate temperature while the flow of the liquid material LM is controlled, and this gas-liquid mixture is passed through the nozzle portion 56 formed adjacent to the gas-liquid mixing chamber 55 inside the main body block 51. Thus, the liquid material LM contained in the gas-liquid mixture is quickly evaporated by depressurization in a stable state.
However, in a conventional liquid material evaporation apparatus, if the flow rate of the carrier gas CG into the gas-liquid mixing chamber 55 is too low, or if the flow rate of the liquid material LM to the gas-liquid mixing chamber 55 is too high, there is a possibility of backflow of the liquid material LM in which the liquid material LM flows into the carrier gas introduction passage 53 and the liquid material LM cannot be evaporated smoothly at high speeds.